CDMA
is a Direct Sequence Spread Spectrum
system. The CDMA system works directly
on 64 kbit/sec digital signals. These
signals can be digitized voice, ISDN
channels, modem data, etc.
Signal
transmission consists of the following
steps:
1.
A pseudo-random code is generated,
different for each channel and each
successive connection.
2.
The Information data modulates the
pseudo-random code (the Information
data is “spread”).
3.
The resulting signal modulates a carrier.
4.
The modulated carrier is amplified
and broadcast.
Signal
reception consists of the following
steps:
1.
The carrier is received and amplified.
2.
The received signal is mixed with
a local carrier to recover the spread
digital signal.
3.
A pseudo-random code is generated,
matching the anticipated signal.
4.
The receiver acquires the received
code and phase locks its own code
to it.
5.
The received signal is correlated
with the generated code, extracting
the Information data.
Courtesy:
Michael Hendry |
